What Causes Black Smoke During Combustion?
2 Answers
Uneven or excessive fuel supply from the high-pressure fuel pump to each cylinder. Uneven fuel supply can lead to unstable engine speed and intermittent black smoke emission. Below are detailed explanations: 1. Overly rich air-fuel mixture: Poor-quality diesel fuel is difficult to ignite, resulting in black smoke emissions from the exhaust. This condition easily causes carbon buildup in the combustion chamber and exhaust muffler. An overly rich mixture leads to incomplete combustion due to high fuel pressure, damaged fuel injectors dripping fuel, poor ignition performance, and inaccurate signals from the coolant temperature sensor, oxygen sensor, air flow sensor, or intake pressure sensor. 2. Cylinder liner: Severe wear of the cylinder liner and piston components. In this situation, piston ring sealing is compromised, leading to a significant drop in cylinder pressure. This prevents diesel from fully combusting, causing black smoke emission and a sharp decline in engine power. In severe cases, the engine may stall automatically under load.
Oh, I've seen this issue quite a few times. It's a common trouble in repair shops when old cars catch fire and emit black smoke. Usually, it's due to improper fuel combustion in the engine, like too much gasoline injection or insufficient air intake. For example, a clogged air filter can cause the fuel mixture to become too rich, the spark plugs fail to ignite, and unburned fuel turns into black smoke. In my lifetime, I've repaired dozens of cars, most starting with old engines, especially those frequently driven at high speeds, which are prone to such problems. Black smoke not only smells bad but also easily catches fire under high temperatures, posing a significant hazard. I remember once a friend's pickup truck almost burned down because of this. It's best to check the air filter's condition before driving and not let it get too dirty. If you do encounter this, turn off the engine immediately and don't move it; get it checked by a professional shop as soon as possible. Long-term neglect can damage the engine, waste fuel, and pollute the environment.
